This invention relates generally to circuit breakers and more particularly, to transmitting current from a movable element of a circuit breaker to a line terminal.
A circuit breaker typically includes a stationary contact and a movable contact located in an arc chamber. The stationary contact is in electric circuit with a first line terminal, and the movable contact is in electric circuit with a second line terminal. For example, the movable contact is coupled to a conductive shaft that is movable towards and away from the stationary contact. The conductive shaft moves relative to the second line terminal, and the electrical connection between the conductive shaft and second line terminal permits such movement while maintaining electrical contact. For example, a spring-loaded finger arrangement can be provided that includes conductive spring-loaded fingers biased into electrical contact with the shaft.
During normal operation, i.e., when no fault occurs, the movable contact is in electrical contact with the stationary contact, and current at a rated level flows through the breaker. Specifically, current at the rate level flows from the first line terminal to the second line terminal via the stationary and movable contacts and the spring-loaded finger arrangement.
Once a fault occurs, the shaft is driven by the trip mechanism so that the movable contact moves away from the stationary contact to interrupt current flow. The spring-loaded finger arrangement permits relative movement of the shaft with respect to the second line terminal yet maintains electrical contact with the shaft. The shaft can be driven so that the movable contact moves towards and into electrical contact with the stationary contact by operating the closing mechanism. The spring-loaded finger arrangement also permits this relative movement of the shaft with respect to the second line terminal while maintaining electric continuity.
In one aspect, a coupler for coupling a movable shaft of a circuit breaker with a line terminal is provided. In an exemplary embodiment, the coupler includes a copper conductive ring having an inner annular wall, and is electrically coupled to the line terminal. A bore extends through the ring, and the bore is sized so that the shaft can extend therethrough.
A plurality of copper bristles extend radially inward from the ring inner annular wall, and the bristles are in electrical contact with the conductive ring. The bristles also are in electrical contact with shaft when shaft extends through ring bore. Specifically, at least some bristles extend sufficiently radially inward from the ring inner wall so that free ends of at least some bristles are in electrical contact with the shaft when the shaft extends through the bore.
In another aspect, a method of assembling a coupler and a movable shaft of a circuit breaker is provided. In an exemplary embodiment, the method includes the steps of aligning the shaft with the bore through the conductive ring, and inserting the shaft through the bore so that at least some bristles are in electrical contact with the shaft shaft. As explained above, the ring is in electrical circuit with line terminal. In operation, as the shaft moves relative to the coupling, the bristles maintain electrical contact between the shaft and the coupling.